Signal transducer for fluidic controls

ABSTRACT

A signal transducer for fluidic controls comprising a deflection chamber into which a fluid is discharged through at least one discharge nozzle and from which emerge outlet orifices for the power fluid jet coming out of the discharge nozzle(s). Heat transfer elements are arranged in the deflection chamber to which control signals can be fed in the form of heat energy to heat and/or cool the element(s) for deflecting the power fluid jet(s).

United States Patent 1191 Rehsteiner Sept. 25, 11973 SIGNAL TRANSDUCER FOR FLUIDIC 3,071,154 1/1963 Cargill et a1. 137/815 CONTROLS 3,187,762 6/1965 Norwood 137/815 3,266,511 8/1966 Turick 137/815 [7 Inventor: Fritz R n E n, 3,276,463 10/1966 Bowles .1 137 815 Liechtenstein 3,283,766 11/1966 HOIIOH 1 137/815 3,417,813 12/1968 Perr 137/815 x [73] Ass'gneei Emwlcklungs'und 3,457,933 7/1969 crafi 137/815 Q E j- Schaan, 3,494,369 2/1970 Inoue 137/815 x Liechten ein 3,509,896 5/1970 Bowles .1 137/815 [22] Filed: Oct. 29, 1971 [21] App]. No.: 193,641

[30] Foreign Application Priority Data Oct. 30, 1970 Austria 9772 [52] US. Cl. 137/828, 235/201 ME [51] Int. Cl. F15c 3/00 [58] Field of Search 137/815; 235/201 ME [56] References Cited UNITED STATES PATENTS 3,557,816 1/1971 Small 137/815 3,540,463 11/1970 Meyer 137/815 Primary Examiner-Samuel Scott Attorney-Watson, Cole, Grindle & Watson [57] ABSTRACT A signal transducer for fluidic controls comprising a deflection chamber into which a fluid is discharged through at least one discharge nozzle and from which emerge outlet orifices for the power fluid jet coming out of the discharge n0zz1e(s). Heat transfer elements are arranged in the deflection chamber to which control signals can be fed in the form of heat energy to heat and/or cool the e1ement(s) for deflecting the power fluid jet(s).

20 Claims, 7 Drawing Figures SIGNAL TRANSDUCER 1 FOR FLUIDIC CONTROLS BACKGROUND OF THE INVENTION In fluid control technique, signal transducers having a deflection chamber into which a fluid jet is discharged which is deflected in the chamber by control signals and emerges outlet orifices are used for carrying out a wide range of control procedures. In known transducers of this type the power jet is deflectedby means of control jets which enter the deflection chamber via control nozzles. Deflection can take place in a continuous manner (analog switch elements) or in the form of a sudden deviation (digital switch elements). By the deflection of the power jet this latter is switched from one outlet nozzle to the other. The operation of the digital switch elements rests on the exploitation of the walladhesion effect in which the power jet flows along and adheres to a straight or curved wall until it is released for example by the effect of a control jet and is deflected into another direction. Analog switch elements on the other hand rely on the momentum exchange between power jet and control jet, the power jet being deflected from a neutral position along the axis of the discharge nozzle by an amount which is proportional to the momentum of the control jet. When the influence of the control jet has come to an 'end the power jet reverts to its neutral position. Both types of switch element are used for carrying out all kinds of control operations.

SUMMARY OF THE INVENTION The invention provides a fluidic transducer comprising a jet deflection chamber into which at least one jet nozzle discharges and from which emerge outlet oriflces for the power-fluid jet from the jet nozzle, and at least two heat transfer elements arranged in symmetrical manner in the deflection chamber in the exit zone verted into pneumaticoutput signals in the form of pressure and/or flow quantity. The heat energy may be positive (heating) or negative (cooling). The signal conversion can be digital or analog-digital. It is known that the deflection of a gas jet can be influenced by heating a curved wall to which it adheres, but this physical effect has hitherto been observed only with asymmetrical arrangements, and problems of zero-point stability and of sensitivity to alien influences occurred.

. In the transducer according to the invention heat energy can be supplied as electrical heat energy or directly in the form of heat radiation, laser radiation or by means of heat conduction. The transducer is particularly suitable for use as input equipment for fluidic controls. It canbe used wherever electric signals are to be converted into fluidic signals, for example in order to link a fluidic control to an existing electrical control, as is the case when equipping available tools with additional accessories, or if a fluidic control is to process input variables which in their nature are thermal or electric, and also in the case of quantity measurements by photoelectric cells or, e.g., when switching cooling fans in furnaces off and on in reply to a temperature measurement, and also with a fluidic automatic pilot if a correcting signal is to be provided in response to the deflection of an electrically read gyro compass.

Preferably the transducer is symmetrical, there being only one convergent-divergent jet-nozzle or at most two nozzles located in symmetrical manner and producing a common resultant power jet. In contrast to the known symmetrical flow elements in which the power jet is adjacent to either one or the other of the nozzle walls, there is also a stable position in the direction of the nozzle axis or axis of symmetry of the nozzles, as long as the Reynolds number of the flow does not ex ceed a critical value dependent on the geometrical shape of the jet nozzle. The exact geometric shape must be established by means of tests. In the case of an arrangement in which a divergent nozzle portion follows a short passage with a constant width, the walls of the former being curved in convex manner with a radius which corresponds to eight times the width of the nozzle, this critical Reynolds number" is about 4,500.

In this embodiment of the invention the power jet can be deflected by heating or cooling without running completely along one wall, and reverts to its stable middle position as soon as the heating or cooling ceases. The angle of deflection of the power jet per heat-output unit comes to about three times the value which is achieved when using an asymmetrical nozzle. As the deflection of the jet under certain flow conditions is substantially independent of outside influences, in particular the flow quantity and the temperature of the power jet, and depends essentially only on the heat energy which is supplied, the result is adequate signal conversion stability. This results in apparatus which is insensitive to outside influences to a large degree and can be used in a wide range of pressure, temperature and vibration.

The-heating elements can consist of heat-conducting plates incorporated into the walls of the deflection chamber. The response time of the transducer is determined essentially by the inertia of the heating elements. In order to achieve quick action the heating plates -should be able to be heated quickly by means of minimal thermal power, and should be able to cool off just as quickly after the supply of heat energy has ceased. This can be achieved by means of heating plates made of metal foil which are joined to an underlayer made of porous material, e.g., deposited by means of evaporation or by electrolytic means. Alternatively the heating plates can be made of metal foil and stretched in a selfsupporting manner over at least one recess in the wall of the deflection chamber. In both cases air is used to insulate the heating elements, as this is not only a very good heat insulator but also has a very small heat capacity per unit-volume in comparison with solid substances. Titanium foils with a thickness of about 4 microns have for example proved to be suitable.

The walls of the deflection chamber comprise preferably at least one substance with good heat-conducting properties in the zone of the heating plates, a heatinsulating intermediate layer can however be provided between the heating plate and the wall of the deflection chamber. The good heat-conducting parts of the wall which are next to the heating plate result in good dissipation of residual heat while the air spaces present behind the plate have a good heat-insulating effect, so that the heat energy which is required in the signal is small. The residual heat is relatively small as almost all the heat produced is transferred to the fluid flow. With this type of construction it was possible to achieve a time constant of about 50 ms, which corresponds to a In an embodiment with a single convergent-divergent jet nozzle two heating elements are preferably located on the walls of the jet nozzle so as to be diametrically opposed to each other. Reliable zero-point stability in the laminar region is achieved by an embodiment in which two jet nozzles which are supplied by means of the same input discharge at an acute angle to each other into a common deflection chamber and in which a heating element is located in the exit region of each jet nozzle. In both cases an analog and a digital method of operation can be achieved. When the jet collection orifices has a sharp-surrounding the result is an analog signal conversion, whereas with horn-shaped expanded collection orifices preferably with rounded entry edges there is a digital signal conversion.

Transducers with three or more collection orifices lying in line in one plane and with a corresponding number of signal outputs can be realized. It is also possible to provide a plurality of collection orifices in a three-dimentional arrangement, e.g., in symmetrical manner and to locate the heating elements in the deflection chamber in spatial distribution around the jet discharge nozzle so-that it is possible to deflect the power jet in a three-dimensional manner. The possible uses of the signal converter according to the invention are therefore numerous and practically unlimited.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is explained in more detail below with reference to the accompanying drawings, in which:

FIGS. 1 and2 show respective embodiments of the signal converter according to the invention in schematic representation;

FIGS. 3, 4 and 5 show details of further embodiments;

FIG. 6 shows another possible embodiment of the invention; and I FIG. 7 shows construction with several output channels in a three-dimensional arrangement.

Throughout the figures, corresponding elements are identified by the same reference numerals.

DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 1 shows an analog transducer 1 consisting of a flat base plate 2 in which channels have been provided, and a flat cover plate which can be placed on the baseplate to cover the channels; this cover plate is omitted from the drawings so that the channels can be seen. The base plate contains a deflection chamber 4 into which discharges a jet nozzle 5 supplied from a fluid inlet 8. The operating fluid will in general be air or some other gas. Facing the nozzle 5, on the opposite side of the deflection chamber, are two collection orifices 6 which communicate with respective output channels 7. Venting channels may be provided, e.g., as shown at 9. The arrangement is symmetrical with respect to the axis of the nozzle 5. The orifices 6 are surrounded by sharp edges, and it will be seen that the fluid issuing from the nozzle 5 can leave the deflection chamber by way of either of the orifices 6, or by way of both orifices in varying proportions, depending on the direction of the jet issuing from the nozzle 5, and accordingly that different pressures or rates of flow can be produced at the respective outlets 7. The sharp edges of the orifices 6 enable the flow to be divided according to the angle at which the jet issues from the nozzle 5, and thereby enable the transducer to operate as an analog device.

The angle of deflection of the jet issuing from the nozzle 5 is controlled by a pair of heat transfer plates 10 incorporated into the walls of the deflection chamber where the nozzle 5 diverges. Conveniently, these plates consist of thin metal foil deposited by evaporation or electrolysis on an underlayer of porous material, and each plate can be independently electrically heated. The base plate 2 preferably is made of materail of good heat conductivity, at least in the region of the plates 10, so that heat can leak rapidly away from the plates when the supply of heat to the plates ceases, so that the thermal inertia of the transducer is small.

Provided that the Reynolds number of the fluid flow in the transducer does not exceed a predetermined critical value, depending on the geometrical shape of the nozzle 5, the jet emerging from the nozzle will have a stable position on the axis of the nozzle. In this condition, the same output will appear in each of the channels 7. Heating or cooling of either of the plates 10 will deflect the jet from its stable central position so that the output in one of the channels 7 will increase and that in the other channel will decrease. When the heating or cooling of the plates 10 ceases, the jet will revert to its stable central position. The angle of deflection of the jet is proportional to the heating power supplied. Heating can be effected in any convenient way, e.g., by means of a heating element.

By means of the transducer shown in FIG. 1, an analog electrical signal can thus be converted into an analog pneumatic signal in the form of pressure and/or quantity of flow.

Although, as indicated above, the working fluid will normally be a gas, the transducer can also operate with a liquid working fluid.

Digital operation can be provided, if the orifices 6 are divergent towards the deflection chamber and do not have sharp edges. FIG. 2 shows another form of transducer, adapted for digital operation in this way. The transducer 1 shown in FIG. 2 also differs from that shown in FIG. 1 in that a pair of symmetrically arranged nozzles 5 are provided, supplied from a common inlet, and discharging at an acute angle to each other into a common deflection chamber 4. The jets emerging from the nozzles 5 effectively form a single jet having a stable central position. Each nozzle 5 is associated wtih a respective heat transfer plate 10, by heating or cooling of which the jets can be deflected to vary the signals appearing in the channels 7. To achieve digital operation, the orifices 6 have rounded edges as shown at 19.

FIG. 3 shows an alternative from of heat transfer plate 10, which is a self-supporting metal foil stretched over a recess 11 in the wall of the deflection chamber 4. As in the case of FIGS. 1 and 2, this plate is intended to be electrically heated. However, to assist dissipation of heat from the plate and thereby to reduce the thermal inertia of the transducer, a duct 12 is provided which connects the recess 11 with the inlet for the operating fluid, and the recess also communicates by way of fence 13 with the surrounding atmosphere. Consequently fluid flows into the recess from a point upstream of the nozzle 5 and carries away heat from the plate 10.

Fluid flow through a recess behind the plate 10 can also be used for heating or cooling the plate 10 to deflect the jet. An arrangement operating in this manner is shown schematically in FIG. 4. The arrangement of the nozzle 5 and plates I is similar to that of FIG. l, but behind each plate 10 is a recess communicating with respective fluid inlet and outlet ducts 14. By means of heating and/or cooling media passed through these ducts, the respective plates 10 can be heated or cooled to control the deflection of the jet issuing from the nozzle 5. In this case, the base plate should be made of a material of poor heat conductivity.

FIG. shows waysin which the plates I0 can be indirectly heated. On the right hand side of the FIG. 5 is shown an electrical heating filament l6 and a lense 17 for directing radiation from the filament onto the associated plate 10. The filament and lense are housed in a bore 15 in the base plate, and the plate it) closes one end of this bore. The input signal in this case is the electrical power supplied to the filament 16, which controls the heat flow through the plate 10 to the jet issuing from nozzle 5, and hence the deflection of the jet.

On the left hand side of FIG. 5, the similar bore is shown housing a laser 18 whose radiation is directed onto the corresponding plate 10.

The transducer may have more than two output channels. FIG. 6 shows a transducer having four such channels, with corresponding sharp-edged orifices 6, in line with each other. Otherwise this embodiment is similar to that of FIG. 1, and operates in an analog manner; by providing the orifices 6 with rounded edges, a corresponding digital transducer could be provided.

FIG. 7 shows a transducer with a three dimensional arrangement of output channels 7. A square arrangement of these channels in a body 3 is shown. As in the case of the transducers shown in FIGS. 1, 2 and 6, these output channels have orifices 6 communicating with a delfection chamber A, and facing a jet nozzle 5. The nozzle is of rectangular cross section and is surrounded by a square arrangement of four heat transfer plates 10 which can be heated or cooled as required. By selectively heating and/or cooling these plates, the jet issuing from the nozzle 5 can be deflected into a selected channel 7, or combination of channels. The output sig nals in the individual channels will depend on the amount of heat energy supplied and the distribution of heating or cooling between the plates 10. The jet will have a stable central position. Depending on the configuration of the orifices 6, the transducer will operate in either a digital or an analog fashion, as already described.

I CLAIM:

l. A fluidic transducer comprising a jet deflection chamber, at least one jet nozzle discharging a power fluid jet into said deflection chamber through at least two outlet orifices emerging from said deflection chamber, at least two non-deformable heat transfer elements mounted symmetrically in said deflection chamber in the exit zone of said at least one jet nozzle, and means for applying control signals in the form of heat energy to heat and/or cool said at least two heat transfer elements for deflecting said powerjet whereby the fluid jet within said at least two outlet orifices is controlled in accordance with said control signals.

2. A transducer as in claim I wherein said heat transfer elements are heated electrically.

3. A transducer as in claim ll wherein said means for applying control signals are indirect heating elements and said heat energy is produced by means of radiation.

4. A transducer as in claim ll having a single convergent-divergent jet nozzle and two heating transfer elements located on the walls of the jet nozzle so as to be diametrically opposite each other.

5. A transducer as in claim ll wherein said outlet orifices have sharp-edge-surrounded entry apertures.

6. A transducer as in claim 1 having a plurality of said outlet orifices mounted in a symmetrical threedimensional arrangement, said at least two heat transfer elements being located in said deflection chamber in spatial distribution around said at least one jet nozzle.

7. A transducer as in claim 1, wherein said at least two outlet orifices are symmetrically mounted with respect to the axis of flow of said at least one jet nozzle, at least one wall of said at least one jet nozzle diverges downstream from the narrowest nozzle cross-section in a convex curve whereby for a fluid flow of a Reynolds number below a predetermined critical value there is a stable position of the power jet in the direction of said flow axis.

8. A transducer as in claim 7 in which said critical value is 1,500 to 5,000.

9. A transducer as in claim 1 wherein said heat transfer elements consist of respective heat-conducting plates incorporated into the walls of said deflection chamber.

10. A transducer as in claim 9 wherein said plates comprise metal foils deposited on a porous underlayer.

11. A transducer as in claim 9 wherein said plates consist of metal foils which are stretched in a selfsupporting manner over recesses in the wall of said deflection chamber.

112. A transducer as in claim 9 wherein the walls of said deflection chamber consist at least in the region of i said plates of a material with good-heat-conducting properties.

13. A transducer as in claim ll further comprising ducts for supplying a heating or cooling medium to the rear side of said heat transfer elements.

14. A transducer as in claim 13 wherein at least one of said ducts connects the associated recess'to a point upstream of said at least one jet nozzle.

15. A transducer as in claim 13 wherein in the region of said plates the walls of said deflection chamber consist of a material with poor heat-conducting properties.

116. A transducer as in claim 13 wherein in the region of said ducts the walls of said deflection chamber consist of a material with poor heat-conducting properties.

117. A transducer as in claim 1 having two jet nozzles discharging into said deflection chamber at an acute angle with respect to each other and fed by the same input, the outer wall of each nozzle being continued from the narrowest nozzle cross-section in a convex curve.

18. A transducer as in claim 17 wherein a heat transfer element is provided in each of said two curved nozzle walls.

19. A transducer as in claim 1 wherein said outlet orifices have hem-shaped expanded entry apertures.

20. A transducer as in claim 19 wherein the entry ap- 

1. A fluidic transducer comprising a jet deflection chamber, at least one jet nozzle discharging a power fluid jet into said deflection chamber through at least two outlet orifices emerging from said deflection chamber, at least two non-deformable heat transfer elements mounted symmetrically in said deflection chamber in the exit zone of said at least one jet nozzle, and means for applying control signals in the form of heat energy to heat and/or cool said at least two heat transfer elements for deflecting said power jet whereby the fluid jet within said at least two outlet orifices is controlled in accordance with said control signals.
 2. A transducer as in claim 1 wherein said heat transfer elements are heated electrically.
 3. A transducer as in claim 1 wherein said means for applying control signals are indirect heating elements and said heat energy is produced by means of radiation.
 4. A transducer as in claim 1 having a single convergent-divergent jet nozzle and two heating transfer elements located on the walls of the jet nozzle so as to be diametrically opposite each other.
 5. A transducer as in claim 1 wherein said outlet orifices have sharp-edge-surrounded entry apertures.
 6. A transducer as in claim 1 having a plurality of said outlet orifices mounted in a symmetrical three-dimensional arrangement, said at least two heat transfer elements being located in said deflection chamber in spatial distribution around said at least one jet nozzle.
 7. A transducer as in claim 1, wherein said at least two outlet orifices are symmetrically mounted with respect to the axis of flow of said at least one jet nozzle, at least one wall of said at least one jet nozzle diverges downstream from the narrowest nozzle cross-section in a convex curve whereby for a fluid flow of a Reynolds number below a predetermined critical value there is a stable position of the power jet in the direction of said flow axis.
 8. A transducer as in claim 7 in which said critical value is 1, 500 to 5,000.
 9. A transducer as in claim 1 wherein said heat transfer elements consist of respective heat-conducting plates incorporated into the walls of said deflection chamber.
 10. A transducer as in claim 9 wherein said plates comprise metal foils deposited on a porous underlayer.
 11. A transducer as in claim 9 wherein said plates consist of metal foils which are stretched in a self-supporting manner over recesses in the wall of said deflection chamber.
 12. A transducer as in claim 9 wherein the walls of said deflection chamber consist at least in the region of said plates of a material with good-heat-conducting properties.
 13. A transducer as in claim 1 further comprising ducts for supplying a heating or cooling medium to the rear side of said heat transfer elements.
 14. A transducer as in claim 13 wherein at least one of said ducts connects the associated recess to a point upstream of said at least one jet nozzle.
 15. A transducer as in claim 13 wherein in the region of said plates the walls of said deflection chamber consist of a material with poor heat-conducting properties.
 16. A transducer as in claim 13 wherein in the region of said ducts the walls of said deflection chamber consist of a material with poor heat-conducting properties.
 17. A transducer as in claim 1 having two jet nozzles discharging into said deflection chamber at an acute angle with respect to each other and fed by the same input, the outer wall of each nozzle being continued from the narrowest nozzle cross-section in a convex curve.
 18. A transducer as in claim 17 wherein a heat transfer element is provided in each of said two curved nozzle walls.
 19. A transducer as in claim 1 wherein said outlet orifices have horn-shaped expanded entry apertures.
 20. A transducer as in claim 19 wherein the entry apertures have rounded edges. 